今 利真

A carboxylic acid‐catalysed transamidation of Boc‐protected diketopiperazines (Boc‐DKPs) was developed in this study, which allowed access to various tripeptides featuring a D‐proline residue in good‐to‐high yields within 30 min. Subsequent coupling reactions between the Boc‐DKPs and di‐, tri‐, and tetrapeptide esters were successfully performed, furnishing the corresponding tetra‐, penta‐, and hexapeptides.

Given the industrial importance of (meth)acrylate esters, various groups have devoted considerable effort to investigating their chemoselective transesterification. In 2021, we developed magnesium(II) and sodium(I) complexes derived from 2,6-di-tert-butyl-p-cresol (BHT-H)...

An organocatalyzed asymmetric aldol reaction of α-keto amides was developed. An N-terminal 4- trans -siloxyproline-based tripeptide with an l - tert -leucine unit adjacent to the 4- trans -siloxyproline residue was used to catalyze the reaction between various α-keto amides and acetone, to produce the corresponding aldol adducts with up to 99% yield and 91% ee.

Here, we report the tripeptide-catalyzed asymmetric aldol reaction between α-ketoesters and acetone under acidic cocatalysts-free conditions. H-Pro-Tle-Gly-OH 3g-catalyzed reactions between α-ketoesters and acetone resulted in up to 95% yield and 88% ee. Analysis of the transition state using density functional theory (DFT) calculations revealed that the tert-butyl group in 3g played an important role in enantioselectivity.

The development of H-Pro-Gly-Ala-OH (3d) to realize an inexpensive and simple organocatalytic system for the direct asymmetric aldol reaction of trifluoromethylated aromatic ketone 1 with acetone was achieved. The 3d-catalyzed aldol reaction of 1a-1j provided various aldol adducts 4a-4j with up to 81% yield and 77% ee. An investigation of the transition state via DFT calculations revealed that hydrogen bonding was important for the revelation of the enantioselectivity.

The development of unnatural tripeptides as highly enantioselective organocatalysts for the asymmetric aldol reaction of isatins was achieved. H-Pro-Gly-D-Ala-OH with the D-alanine residue as the C-terminal amino acid residue expressed the best enantioselectivity. The H-Pro-Gly-D-Ala-OH-catalyzed reaction of isatins gave various aldol adducts with up to 93% yield and up to 97% ee. Investigation of the transition state via DFT calculation revealed that high optical purity was realized by the D-alanine controlled steric environment.

The Ru-catalyzed dehydrogenative silylation of 2-alkyloxazolines with 1,1,1,3,5,5,5-heptamethyltrisiloxane took place site-selectively at methyl C(sp3)−H bonds located γ to the nitrogen atom of the oxazolyl groups. Pyridine and pyrazole rings could also be used as a directing group. A catalytic mechanism based upon successive σ-bond metathesis is proposed.